Análise comparativa de comunidades de pequenos mamíferos em fragmentos de Mata Atlântica ligados por um corredor agroflorestal no município de Seropédica, RJ

Abstract

The process of habitat fragmentation is one of the main causes of species extinction and loss of biological diversity. To minimize the negative effects of this process it is fundamental the development of strategies to restore the structural and functional connectivity among fragments, to reestablish or to facilitate the flow of organisms, seeds or pollen. This work had as objective to compare the composition of small mammal communities among different habitats in a fragmented landscape and to analyze the role of an agroforestry corridor in the movement of individuals between fragments. Additionally, a comparison of the efficiency of capture of small mammals with Sherman traps (XLF15 model, 10x11.5x38 cm) in two positions (at ground and on trees) and pitfall traps (65 l, 40 cm in diameter and 60 cm in depth) was done. The study was carried out in an area located at the Fazendinha Agroecológica, EMBRAPA Agrobiologia, Seropédica, RJ, composed by two fragments (fragment of the slope [FB] and fragment of the top [FT], with 8 ha and 17 ha respectively), linked by a agroforestry corridor (C) and surrounded by a matrix of pasture (P). The samplings were carried out monthly from October 2008 to October 2009, totaling 13 sessions of capture with four consecutive nights. All traps were baited with a mixture of banana, oat, bacon and peanut cream. To compare the capture success among trap types and among the studied habitats (FT, FB, C and P) Qui-squared tests were used. A total of 155 captures from 137 individuals pertaining to 6 species were obtained. The pitfalls had 88 captures (56.8%) of four species, having a success significantly higher than the Shermans at ground with 45 (29.0%) of five species and Shermans at trees with 22 (14.2%) of two species (X2 = 6.50, p = 0.040). This result indicates that the combination of different types of traps can increase the total success of capture and make possible the acquisition of data more representative of the studied community. Regarding the use of the different habitats, the higher capture success was in FT, followed by FB, P and C (χ2 = 81.04, p <0.0001). Considering the marsupials and rodents separately, for both groups the fragments had the higher capture success. However, the marsupials presented higher success of capture in the corridor that in the pasture (χ2 = 77.67, p <0,0001) while the rodents were more captured in the pasture than in the corridor (χ2 = 21.620, p <0,0001). Nonetheless, in these habitat, only Akodon cursor had more than one individual caught, suggesting that this habitat is hostile for most of the species captured in this study. In spite of none movement between fragments has been detected, the corridor was used by two species of marsupials (Didelphis aurita and Philander frenatus) and three of rodents (A. cursor, Mus musculus and Oligoryzomys nigripes). These results suggest that it is used as habitat or foraging area by these species, and could potentially favor the movement of individuals between fragments.